A heat exchanger is a piece of equipment for efficient heat transfer from one medium to another. One such heat exchanger is a heat exchanger for thermoelectric power generation as illustrated in FIG. 1. Referring to FIG. 1, FIG. 1 illustrates a conventional thermoelectric power generator 100 that includes an exhaust gas heat exchanger 101. Exhaust gas heat exchanger 101 is defined by an exhaust housing/wall 102, such as an aluminum exhaust housing. Exhaust gas heat exchanger 101 receives a pressurized exhaust gas stream 103 from an internal combustion engine 104 and extracts thermal energy from exhaust gas stream 103.
Exhaust gas heat exchanger 101 may include a flange (not shown) to sealingly connect to an exhaust pipe (not shown) of internal combustion engine 104. The flange and wall 102 may be formed from a single piece, by, for example, upsetting. Alternatively, the flange may be attached to wall 102 by welding, brazing, or crimping. It is to be understood that the exhaust gas stream 103 from internal combustion engine 104 is at a higher pressure than the ambient atmosphere when the engine 104 is running and the pressurized exhaust gas stream 103 is contained in an exhaust system.
Exhaust gas heat exchanger 101 may include fins 105A-105R (e.g., aluminum fins) that are in contact with wall 102 to increase the rate of heat transfer from exhaust gas stream 103. Fins 105A-105R may collectively or individually be referred to as fins 105 or fin 105, respectively.
Thermoelectric power generator 100 further includes thermoelectric device modules 106 with their hot-side connected to wall 102. Thermoelectric device modules 106 are configured to convert the thermal energy extracted by heat exchanger 101 to electrical energy 107 for consumption or storage by an electrical load 108 (e.g., batteries, electric motors, fans).
Furthermore, thermoelectric power generator 100 includes liquid cooled heat exchangers 109A, 109B disposed on the cold-side of thermoelectric device modules 106 to transfer the thermal energy from thermoelectric device modules 106 to a liquid coolant (e.g., water) passed through liquid cooled heat exchangers 109A, 109B.
Currently, conventional thermoelectric power generators, such as disclosed in FIG. 1, utilize a metal wall, such as wall 102. However, by utilizing such a metal wall, there exists thermal contact resistance between metal wall 102 and the hot-side of thermoelectric device modules 106. As a result, conduction losses occur thereby lessening the effectiveness of the thermal energy transferred to thermoelectric device modules 106 from heat exchanger 101.
Furthermore, a source of failure for conventional thermoelectric power generators occurs at the bond between the metal wall, such as wall 102, and the hot-side of the thermoelectric device modules, such as modules 106. Such a failure occurs because of the large differences in the coefficient of thermal expansion between the metal wall and the ceramic materials used on the hot-side of the thermoelectric device modules thereby resulting in thermal fatigue failure of the bond between the wall and the thermoelectric device modules.
As a result, such conventional thermoelectric power generators are subject to conduction losses and thermal fatigue failures.